The invention is directed to a cushioning apparatus for a railway car, and more particularly to a selective travel apparatus that absorbs draft and buff loads applied to a coupler of a railway car.
As is generally known, railway cars are connected to an adjacent car by a coupler. The coupler is joined to a yoke, for example an “E-type” or “F-type” yoke, by a draft key or pin, and the assembly is mounted in a railway car center sill.
To prevent damage to the railway cars and the laded goods during operation, and especially during assembly of the railway car train in the yard, various devices have been installed to absorb loads on the coupler so that impact forces are not transmitted to the railway car.
In a conventional frictional draft gear, one or more elastic elements, such as a coil spring or a set of elastomeric pads, is enclosed in a housing mounted in the yoke behind the coupler. A piston-like element frictionally received in the housing absorbs buff loads transmitted via a coupler follower which moves inside the yoke in response to buff impact force applied on the coupler, and the draft gear is compressed in the yoke in response to draft loads. The basic draft gear apparatus has been used for decades. However, in many cases unacceptably large forces are transmitted to the railway car.
A hydraulic cushioning unit comprises a piston received in a cylinder filled with fluid. Such devices may dissipate more force than a conventional draft gear, but they are known to be prone to leakage.
U.S. Pat. No. 2,766,894 describes a selective travel draft gear with separate cushioning elements for buff and draft loads on the coupler. In this design, both of the cushioning elements are located forward of the back wall of the yoke.
U.S. Pat. No. 2,825,472 describes a selective travel draft gear which comprises separate cushioning elements for buff and draft loads on the coupler, but both stacks of cushioning elements are attached to the yoke.
U.S. Pat. No. 6,446,820 discloses a selective travel draft gear of more recent vintage where the separate draft and buff cushioning elements are coupled and adapted to fit into the draft gear pocket. These apparatuses have not been very well received, and may be prone to buckling, wherein a stack of elastomeric elements is pushed out of alignment and fails to operate according to specifications.
All of the above-referenced U.S. Patents are incorporated by reference.